Combining Exception Handling and Replication for Improving the Reliability of Agent Software

Abstract. Exception handling and replication are two complementary mechanisms that increase software reliability. Exception handling helps programmers in controlling situations in which the normal execution flow of a program cannot continue. Replication handles system failures through redundancy. Combining both techniques is a first step towards building a trustworthy software engineering framework. This paper presents some of the results from the Facoma project. It proposes the specification of an exception handling system for replicated agents as an adaptation of the Sage proposal. It then describes its implementation in the Dimax replicated agent environment

Specification of an Exception Handling System for a Replicated Agent Environment

Exception handling and replication are two mechanisms that increase the reliability of applications. Exception handling helps programmers to control situations in which the normal flow of a program execution cannot continue. Replication handles system failures. Exceptions handling and replication do not apply to the same situations and are two complementary mechanisms to increase the reliability of applications. Moreover, each technique can benefit from the other: exception handling capabilities can rely on replication mechanisms while replication can be further secured by using exceptions. The paper proposes a specification of an execution history oriented exception handling system for an agent language and middleware providing replication. The paper proposes an original signaling algorithms taking into account replicated agents and a rationale of how exception handling and replication mechanisms can combine to increase the capability of programmers to achieve reliable agent-based applications. 1